Conventional riflescopes and other telescopic sights accomplish magnification changes by optical elements that are either movable along the optical path, or that are switched into and out of the optical path. Also known are sight designs utilizing switching mirrors and/or beam splitters for switching between one of two different optical systems alternately viewable through a common eyepiece. Some sights include optical paths for day and night operation, including visible and infrared channels, which may be combined and superimposed for viewing as a composite image. In many of these systems, components of the sight must be manually moved to switch between viewing modes, which makes the sight more complicated, prone to image instability or misalignment, cumbersome and slow for switching between modes, and prone to making noise.
U.S. Pat. No. 2,388,673 of Brown, U.S. Pat. No. 2,512,153 of Henvey et al., and U.S. Pat. No. 2,527,719 of Greenstein et al. describe dual optical power split-field telescopic sights utilizing different lenses or lens segments for upper and lower portions of the optical system. These telescopic sights utilize complex lens systems and optical prescriptions, and are limited by a shared eyepiece through which both fields are simultaneously viewed.
The present inventors have recognized a need for an aiming system that facilitates viewing a target scene through a telescopic sight and through a second sight having a different field of view or aiming capability, such as a non-magnifying reflex sight providing a wide field of view, very little field obstruction, and fast target acquisition. Various known systems utilize a miniature reflex sight (also known as a red-dot sight) mounted atop a telescopic sight, but the height of the viewing region of the reflex sight in such systems is generally much higher than the exit pupil of the telescopic sight and too high for achieving a cheek weld with the rifle stock (buttstock) as is desirable for stable aiming. Substantial head movement is also needed to switch between the two sights. The required head movement can be cumbersome and slow, particularly when switching from the reflex sight to the telescopic sight and re-aligning the eye with the typically small exit pupil of the telescopic sight.